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Full text of "Surtigas, S. A., tank-semitrailer overturn, explosion, and fire, near Eagle Pass, Texas, April 29, 1975"




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NATIONAL 

TRANSPORTATION 

SAFETY 

BOARD 

WASHINGTON, D.C. 20594 

HIGHWAY ACCIDENT REPORT 

SURTIGAS, S. A., 
TANK-SEMITRAILER OVERTURN, 
EXPLOSION, AND FIRE 



NEAR EAGLE PASS,TEXAS 
APRIL 29, 1975 

REPORT NUMBER : NTSB-HAR-76-4 



UNITED STATES GOVERNMENT 



TECHNICAL REPORT DOCUMENTATION PAGE 



1 . Report No. 

NTSB-HAR-76-4 
k. Title and Subtitle 



2. Government Accession No. 



Highway Accident Report - 
Surtigas, S.A. , Tank-semitrailer Overturn, Explosion, 
and Fire, Near Eagle Pass, Texas, April 29, 197S 



7. Author(s) 



9. Performing Organization Name and Address 

National Transportation Safety Board 
Bureau of Surface Transportation Safety 
Washington, D. C. 20594 



12. Sponsoring Agency Name and Address 

NATIONAL TRANSPORTATION SAFETY BOARD 
Washington, D. C. 20594 



3. Recipient 's Catalog No. 



5. Report Date 
May 5. 1976 



6. Performing Organization 
Code 



8. Performing Organization 
Report No. 



10. Work Unit No. 
1801A 



11. Contract or Grant No. 



13. Type of Report and 
Period Covered 

Highway Accident Report 
April 29, 1975 



14. Sponsoring Agency Code 



15. Supplementary Notes 



16. Abstract ~~ 

At 4:20 p.m. on April 29, 1975, a Surtigas, S.A., tractor-tank-semitrailer, west- 
bound on U.S. Route 277 near Eagle Pass, Texas, swerved to avoid an automobile ahead 
which was slowing for a turn. The tank-semitrailer separated from the tractor, struck 
a concrete headwall, and ruptured; vaporized LPG was released. The ensuing fire and 
explosion destroyed a building and 51 vehicles. The 51 persons who were in the area 
were burned and 16 persons, including the truckdriver, were killed. 

The National Transportation Safety Board determines that the probable cause of 
this accident was the evasive action taken by the truckdriver to avoid a slowing 
vehicle in his path of travel. The cause of the fatalities and injuries to persons 
in the vicinity was the explosive force and fire, from which they had no time to 
escape. The rapid development of the explosive force and fire was caused by the 
gross rupture of the tank. 

As a result of its investigation of this accident, the National Transportation 
Safety Board made recommendations to the Federal Highway Administration, the Texas 
Department of Highways and Transportation, and the Department of Transportation. 



17. Key Words 

Butane; propane gas; LPG; explosion; fire; center of 
gravity; vehicle rollover; tank rupture; burn victims; 
vaporized gas. 



19. Security Classification 
(of this report) 
UNCLASSIFIED 



20. Security Classification 
(of this page) 
UNCLASSIFIED 



18. Distribution Statement 
This document is available 
to the public through the 
National Technical Informa- 
tion Service, Springfield, 
Virginia 22151. 



21 .No. of Pages 
19 



22. Price 



NTSB Form 1765.2 (Rev. 9/74) 



TABLE OF CONTENTS 

Page 

SYNOPSIS 1 

INVESTIGATION 2 

The Accident 2 

Injuries to Persons 3 

Vehicle Information 5 

Driver Information 7 

Survival Aspects 7 

Other Information 9 

ANALYSIS 10 

The Accident 10 

Fixed Roadside Objects 11 

Risks in LPG Transportation 13 

CONCLUSIONS ". 14 

Findings 14 

Probable Cause 15 

RECOMMENDATIONS 15 

APPENDIX — Investigation 17 



NATIONAL TRANSPORTATION SAFETY BOARD 
WASHINGTON, D. C. 20594 

HIGHWAY ACCIDENT REPORT 

Adopted: May 5, 1976 

SURTIGAS, S.A., TANK-SEMITRAILER OVERTURN, 

EXPLOSION, AND FIRE, NEAR EAGLE PASS., TEXAS 

APRIL 29, 1975 

SYNOPSIS 

At 4:20 p.m. on April 29, 1975, a Surtigas, S.A. , tractor-tank- 
semitrailer, westbound on U.S. Route 277 near Eagle Pass, Texas, swerved 
to avoid an automobile ahead which was slowing for a turn. The tank- 
semitrailer separated from the tractor, struck a concrete headwall, and 
ruptured; vaporized LPG was released. The ensuing fire and explosion 
destroyed a building and 51 vehicles. The 51 persons who were in the 
area were burned and 16 persons, including the truckdriver, were killed. 

The National Transportation Safety Board determines that the probable 
cause of this accident was the evasive action taken by the truckdriver 
to avoid a slowing vehicle in his path of travel. The cause of the 
fatalities and injuries to persons in the vicinity was the explosive 
force and fire, from which they had no time to escape. The rapid develop- 
ment of the explosive force and fire was caused by the gross rupture of 
the tank. 



- 2 - 

INVESTIGATION 

The Accident 

At 4:20 p.m. on April 29, 1975, a Surtigas, S.A., tractor-tank- 
semitrailer (truck) was, westbound on U.S. Route 277 transporting 8,748 
gallons of liquid propane gas (LPG) from Big Wells, Texas, to Piedras 
Negras, Mexico. According to witnesses, as the truck approached Eagle 
Pass, Texas, at an estimated speed of 50 to 55 mph, its driver braked 
and swerved sharply to his left to avoid a white automobile ahead which 
had suddenly slowed to turn off of the road. As the truck crossed into 
the eastbound lane, the truckdriver steered to the right to return to 
the westbound lane and to avoid three eastbound automobiles. The right 
turn was so severe that the tractor and semitrailer began to overturn to 
the left. In an effort to resist the overturn, the driver steered to 
the left; however, the semitrailer continued to overturn. One hundred 
and eight feet east of an irrigation canal, the semitrailer separated 
from the tractor, overturned, slid across the road and the shoulder of 
the east lane, and struck an unprotected concrete headwall of the irriga- 
tion canal. 

After the trailer had separated, the tractor remained upright and 
rolled into the west lane; the driver remained in the cab. The tractor 
stopped or was stopping near the semitrailer when the tank struck a 
headwall and ruptured. The tank separated into two parts and pressurized 
LPG was released through the opening. Several witnesses described a 
noise which resembled that of a violent wind storm, followed immediately 
by an explosion. Simultaneously, fire covered the area, and a second 
explosion was heard. The explosive forces separated the tractor cab 
from its chassis and blew it to the north; the driver remained in the 
cab. The chassis was snagged by a tank appurtenance and was propelled 
136 feet west onto the shoulder of the eastbound lane. 

After the tank broke into two pieces, the large forward section of 
the tank was propelled into the air, where it struck an elevated sign; 
traveled 1,029 feet and struck the ground; bounced into the air and 
traveled 278 feet; struck and demolished a mobile home; bounced back 
into the air and traveled 347 feet over a second mobile home, which 
burst into flames and was destroyed; struck a third mobile home and came 
to rest 1,654 feet from its point of departure. The fire in the second 
mobile home was attributed to the failure of an LPG tank in the mobile 
home. 

The aft section of the tank split into three parts. The three 
parts rocketed through the air with the semitrailer suspension, traveled 
an average of 800 feet to the east and to the northwest, and fell to the 
ground. 

Six occupants in two of the eastbound cars were overtaken by the fire 
and burned badly after they fled their vehicles. The used-car facility and 



- 3 - 



50 vehicles parked In front of the facility were destroyed by the explosion 
and the fire. Forty-four persons, both inside and outside the building, 
were knocked down and burned. 

U.S. Route 277 was a two-lane, 40-foot-wide concrete roadway with a 
well-worn asphalt surface. (See Figure 1.) The eastbound and westbound 
lanes were divided by a double yellow centerline, which was also worn. 
The road crossed an irrigation canal at the accident site. Four hundred 
and thirty-one feet east of the irrigation canal, the roadway was intersected 
by U.S. Route 57. Near its intersection with Route 57, Route 277 widened 
and its lanes were separated by a raised concrete divider. There were 
30-foot gravel and clay shoulders on each side of the roadway. The 
posted speed limit was 50 mph. The westbound truck approached the site 
on an average 1.70-percent downgrade. On the day of the accident, the 
visibility was 5 miles and the temperature was 80 degrees. Witnesses 
described traffic as light but steady. 

A used-car facility was located 200 feet east of the intersection 
with Route 57, north of the roadway and east of the irrigation canal. 
North of this facility was a large fenced lot which contained wrecked 
and disassembled vehicles. South of the roadway and west of the canal 
to the Eagle Pass city limits were four businesses widely separated by 
open fields. Inside the city limits, south of the roadway, was a 
trailer park. The 50 vehicles parked on the shoulder of the westbound 
traffic lane denied a clear escape area for westbound traffic. The 
evasive maneuvers of the truck took place in the vicinity of this 
congestion. 

The irrigation canal which ran north and south under the roadway 
had concrete headwalls 28 feet to the north and 29 feet to the south of 
the roadway's edge. The concrete headwalls were 17.5 feet long, 12 
inches thick, and 23 Inches high, and constructed of reinforced concrete. 
They were not protected by a barrier. 

Injuries to Persons 



Injuries Driver Passengers Other 

Fatal 10 15 

Nonfatal GO 35 

None 







4 isi::Sg ill lli$ 



.If i||Lilili|5^p3 Pill iiii 
iiiiiyilHlis-iliillliiillllSiiiiiii 



sSijtiiiaKiiiiaaassa 



- 5 - 



Vehicle Information 



The vehicle was a tractor-semitrailer (MC-330 tank) combination 
owned by Surtigas, S.A. , a private foreign carrier located in Sabinas 
Mexico. The weight of the vehicle was as follows: 



lbs 



Tractor 


14,000 


Trailer 


19,353 


Cargo 


40,095 



Total 73,448 

The Tractor — The tractor was a three-axle, 1972 International 
Harvester, cab-behind-engine, equipped with a Cummins 'NHC250 diesel 
engine, a 10-speed Fuller transmission, a Hendrickson bogie, and a 
Fontaine sliding fifth wheel (serial No. 437472Y030149) . The Fontaine 
fifth-vheel assembly consisted of the fifth wheel, the slide plate and 
the frame mounting plate. * 

The fifth wheel was found attached to the trailer king pin. The 
vertical flange of the fifth-wheel plate, adjacent to the fifth-wheel 
cross-shaft, was bent outward. (See Figure 2.) The slide plate was 
found 50 feet south of the tractor. The transverse tube through which 
the fifth-wheel cross-shaft normally is positioned was bent upward and 
was disconnected from its right-side attachment. The metal failed in 
the weld. The fore-and-aft positioning plunger was flush with the bottom 
of the slide plate. (See Figure 3.) 

The mounting plate was attached to the tractor frame's slide rails 
and was twisted slightly in conformance with the frame distortion. The 
rearmost fifth-wheel positioning slot showed evidence of wear at the 
rear edge of the slot. Neither the left or right slide channels were 
distorted. 

The cab and other sheet metal components had been blown off the 
tractor during the initial explosion. The transmission shift tower was 
missing. The transmission shift rails were found in "neutral." The 
left-side fuel tank was attached to the left-side rail. The right-side 
fuel tank was found 38 feet west of the tractor frame. The tractor 
frame was bent downward. The left-side rail's upper flange and top web 
section were torn. The steering gear functioned normally. The rear 
bogie axle top-mounted torque arm had failed in back of its crossmember 
attachment. 

The brake linings measured about 1/2 inch at each wheel. This was 
the only brake adjustment that could be examined, and it was within 
acceptable limits. The other brake systems had been so badly distorted 
that their adjustments could not be evaluated. Postcrash inspection of 
the tandem axles did not reveal any defects that may have contributed to 
the loss of control and the vehicle's upset. 



6 - 




Figure 2. Fountalne fifth wheel 
still attached to front section of 
tank after the accident. 




Figure 3. Fifth-wheel slide plate 
as it was found 50 feet north of 
the tractor chassis. 



- 7 - 



Tank-semitrailer — The tank-semitrailer was a 1965 MC-330 Tatsa 
tank manufactured by the Lubbock Manufacturing Company. It had a 
10,000-gallon water capacity with a design pressure of 250 psi at 150°F. 
The shell was manufactured in accordance with 49 CFR 178.336 from U.S. 
Steel T-1 (ASME Code Case No. 1204-11). The tank was 35 feet 8 inches 
long and had an 86-inch inside diameter and a thickness of 0.376 inch 
(min) . The tank heads had a thickness of 0.250 inch. 

Each of the sections of the tank shell had scratch marks on the left 
side. The tank's right-rear side, left side, and a section of the rear 
head each contained impact marks. Impact also was evident on the forward 
22.8 feet of the tank. 

The open end of the forward section of the tank was deformed into an 
ellipse. (See Figure 4.) The edges of the failure area had a mechanically 
deformed, gouged, and stretched dent. The dent was located on the right 
side of the tank, 26 inches from the top longitudinal centerline and 22 feet 
9 inches rearward of the front head-to-shell weld. At the point of impact, 
the shell material was gouged from an original thickness of 0.387 inches 
to 0.279 inches. The internal tank pressure of 87 psig combined with 
the impact load to cause a sheer-type failure around the tank circumference. 
The pressure, acting upon the tank material at the point of initiation 
of the crack, produced the extensive spread of the initial crack and 
permitted the violent rupture and separation of major parts of the tank. 

The Safety Board analyzed a sample of the metal from the suspected 
impact area, and found no evidence of a preexisting crack. The analysis 
showed that the fracture appeared to be caused by an overload separation. 

The Cargo — The truck was transporting 8,748 gallons of LPG (4,374 
gallons of butane and 4,374 gallons of propane). During transportation, 
the gases were maintained in a liquid state under pressure. The vapor 
pressure of this cargo was about 87 psig at 80°F ambient temperature. 

Driver Information 

The 35-year-old truckdriver was a resident of Colonial, Piedras 
Negras, Mexico, and had been hired by Surtigas, S.A., as a relief driver 
3 months before the accident. He did not have the medical certificate 
required by the Federal Motor Carrier Safety Regulations; however, it was 
reported that he had a valid Mexican driver's license. The Safety Board 
could not determine the driver's experience or his driving record. 

Survival Aspects 

Emergency medical assistance at the accident scene was rendered by 
personnel from the Maverick County Hospital, Eagle Pass, Texas, and local 
rescue units. Thirteen persons were treated and released, and 12 were 
hospitalized. Three persons, including the truckdriver, were pronounced 
dead at the hospital. The truckdriver died as a result of a crushed 
skull. 



- 8 - 




Z liu X 




c=^ 





Six helicopters provided by the 507th Medical Company, Fort Sam 
Houston, Texas, transported 22 seriously burned persons to burn treatment 
centers in San Antonio. The first persons arrived in San Antonio at 
9 p.m., and the last arrived at 1:30 a.m. on April 30, 1975. 

Other Information 

LPG Operator — Surtigas transports flammable gas in cargo tank 
vehicles within a 150-mile-radius of its facility; the area includes 
Eagle Pass. Surtigas operates on both sides of the United States- 
Mexican border. The carrier had not been served with a copy of the 
Federal Motor Carrier Safety Regulations (FMCSR) nor had it been subject 
to any compliance inspections; however, while in the U.S., the carrier 
and the driver were subject to FMCSR' s. The company vehicle maintenance 
and driver records were not available for examination. Neither the vehicle, 
the driver, nor the company were in compliance with all applicable FMCSR' s. 

Applicable Regulations and Guidelines — The FHWA Highway Safety 
Program Standard No. 12, "Highway Design, Construction, and Maintenance," 
states: 

"Every State shall have a program. . . (which) shall provide as a 
minimum that... (J) There are highway design and construction features 
whenever possible for accident prevention and survivability including 
at least the following: 

1. Roadside clear obstacles, with clear distance being 

determined on the basis of traffic volumes, prevailing 
speeds, and the nature of development along the street or 
highway. . . 

3. Protection devices that afford maximum protection to the 

occupants of vehicles wherever fixed object cannot reasonably 
be removed or designed to yield." 

The manual for Standard No. 12 expands the Standard by stating: 

"Whenever practical it is desirable that a driver control recovery 
area clear of obstructions for a distance of 30 feet or more from 
the edge of the traveled way, be provided in rural areas." 

In its guidelines for the design and location of culverts, the 
American Association of State Highway and Transportation Officials 
(AASHTO) states that "If headwalls and endwalls are required, they 
should be designed not to protrude above the ground line." 1/ 



\l Standard Specifications for Highway Bridges, AASHTO, 1973, Section 
~ 1.1.5, Culvert Location and Length. 



- 10, - 



AASHTO further recommends that "culvert headwalls . . . should be placed an 
adequate distance from the main lanes of travel or shielded from errant 
vehicles." ll 

The Federal Highway Administration (FHWA) recommends that "Headwalls 
or culvert ends should be constructed flush with the adjacent embankment 
to avoid a projecting fixed object." "ij FHWA also recommends that if 
fixed objects cannot be removed, they should be protected by devices 
such as guardrails. 

At the time of this accident, the Department of Transportation 
(DOT) had not prescribed requirements for registration of carriers of 
hazardous materials. However, the provisions to' require the company to 
register now exist in Public Law 93-633, Title I - Hazardous Materials, 
dated January 3, 1975. Section 106(b) states that each person who 
transports or causes to be transported or shipped it} commerce hazardous 
materials... "may be required to submit to the Secretary a registration 
statement not more often than once every 2 years. The registration 
statement shall include the person's name, principal place of business, 
a complete list of hazardous materials handled, and an averment that 
such person is in compliance with all applicable criteria established by 
the Act." 



ANALYSIS 



The Accident 



After the accident, witnesses were questioned concerning the accident. 
Five occupants of three eastbound cars stated that they saw the truck 
coming toward them; that it was following a white automobile; that the 
white automobile suddenly slowed down to turn into the used car facility; 
that the truck swerved around the car and then back into its own lane of 
traffic and then turned over. The witnesses do not recall seeing a turn 
signal from the automobile. The other occupants, farther from the 
truck, did not mention the white automobile, but did see the truck 
swerve first to the left, then to the right, and then turn over. 

Despite extensive investigation by the Safety Board and the Texas 
Department of Public Safety, the white automobile could not be located 
after the accident. 

The truckdriver had no alternative but to swerve to the left. The 
right shoulder, which would have served as a recovery area, was occupied 
by vehicles. FHWA Highway Safety Program Standard 12 recommends that 
high-speed roads have a clear recovery area of 30 feet on each side of 

Ij Highway Design and Operational Practices Related to Highway Safety, 

Second Edition, 1974, AASHTO. _ 
"ij Handbook of Highway Safety Design and Operating Practices, FHWA, 

Section E2, Culvert and Bridge Structure. 



- 11 - 

^Pie road and that fixed objects which cannot be removed be protected by 
barriers. At this site, the raised portion of the culvert's headwall 
should have been protected and the 50 parked automobiles should have 
been prohibited. 

If the Texas Highway Department or the Maverick County Highway 
officials do not see fit to modify the headwall and prohibit the presence 
of the parked vehicles in the recovery area, they should reduce the speed 
limit to one considered safe under such conditions. If the truck had 
been traveling at 30 to 40 mphj its evasive maneuver may not have been 
necessary or would not have resulted in its upset. 

As the truckdriver turned the tractor to the right to return to the 
westbound lane, he also was braking, which reduced his j speed slightly. 
The high center of gravity was acted upon by the centrifugal forces from 
the right turn, and the tank-semitrailer began to overturn. As the 
trailer continued to upset to the left, the tractor frame was twisted 
and the- fifth-wheel mounting plate was deflected. The distortion was of. 
sufficient magnitude that the fore-and-aft position plunger in the slide 
plate pulled out of the tractor's mounting-plate slot. As the trailer 
continued to turn over, it also was sliding toward the rear of the 
tractor. At some point, the air hose from the tractor-trailer brake 
either broke or became disconnected and the trailer brakes came on 
automatically. With the left-side trailer wheels still in contact with 

I the road surface, there was sufficient braking to pull the unrestrained 
trailer from the tractor. The front of the trailer dropped to the 
southerly edge of the roadway — 108 feet from the canal. 

When the trailer separated from the tractor, the upsetting forces 
on the tractor were removed. The tractor dropped onto its right wheels, 
continued westward, and stopped opposite the headwall of the irrigation 
canal. The trailer rolled onto its left side and slid toward the concrete 
headwall and struck it. (See Figure 5.) 

At impact, the tank shell was gouged severely and was forced into 
an elliptical shape. Impact forces also caused the tank to rotate 
counterclockwise about 40 to 50 degrees and to rebound to the south edge 
of the eastbound lane. The tank shell began to crack where it struck 
the headwall. The internal tank pressure of 87 psig combined with the 
impact load to cause a shear-type failure around the circumference of 
the tank. 

Fixed Roadside Objects 

If highway design and construction standards and AASHTO recommended 
practices had been followed in the construction or remodeling of the 
concrete headwall, it would have been flush with the ground and the tank 
would not have ruptured. If remodeling of the headwall was not possible, 
it should have been protected by a barrier. Even though the truck might 
have penetrated the barrier, the barrier might have at least absorbed 



I 



- 12 - 




CONCRETE HEADWALL 
OVER 
IRRI CATION CANA L 



SHOULDER CONTACT AT IMPACT 



FIGURES. CALCULATED ATTITUDE OF 
TANK-SEMITRAILER AT 
IMPACT WITH CONCRETE 
HEADWA LL 



- 13 - 

^nough energy or redirected the tank to prevent the rupture of the tank 
"shell. The FHWA and AASHTO should encourage the States to consider such 
hazards In the development of their spot improvement programs. 

Risks in LPG Transportation 

The pressurized LPG and the large quantity of the hazardous material 
being transported contributed to the severity of this accident. The 
pressure of the compressed LPG provided a portion of the energy needed 
to produce the abrupt, massive breakup of the cargo tank after it was 
ruptured. That pressure also contributed to the rocketing of the tank 
parts after they separated and to the rapid dispersion of vaporized LPG 
from the shattered tank. When the tank integrity was lost, much of the 
pressurized liquid changed into a gaseous form and was propelled away 
from the tank by the expanding gas. 

The injuries and property damage which followed the breakup of 
the container could have been reduced in several ways. The size of the 
area endangered by the vapors and subsequent fires can be reduced if the 
quantity of LPG in the container which breaks apart is reduced. For 
example, had the LPG shipment been packaged in smaller containers, such 
as cylinders, it is unlikely that any fatal injuries would have occurred. 
The size of the affected area can also be reduced by limiting the rate 
at which the cargo tank breaks apart or the rate at which the contents 
are released and dispersed. For example, if LPG were transported in a 
^elf-refrigerated form and at ambient pressures, the rate of tank breakup 
would be reduced and the rate of material vaporization and dispersion 
would be reduced. These modifications could provide victims additional 
time to react to the threat of dispersing LPG. 

However, technical methods of modifying the form and quantity of 
LPG transported have not been explored fully, possibly because the 
problem of modifying the behavior of liquefied, pressurized flammable 
gases has not been defined precisely in engineering terms. 

Until a feasible method can be found to give potential victims more 
time for survival, a reduction in the risks will depend on improvements 
in the following area: 

Compliance with safety regulations — There is no evidence to 
indicate that lack of compliance with safety regulations was causative 
in this accident. However, the accident revealed that compliance with 
safety regulations by the carrier was not assured because the carrier 
was not known to the Bureau of Motor Carrier Safety nor was he served 
with a copy of the Federal Motor Carrier Safety Regulations. The small 
Federal enforement staff responsible for assuring compliance with the 
safety regulations was not aware of the Surtigas operations. After the 
accident, the compliance staff made roadchecks at border crossing points 
to identify other LPG carriers and to assure that they were aware of the 
regulatory requirements with which they had to comply. 



- 14 - 



The Safety Board believes that these carriers would be identified 
more effectively if registration statements were required, for safety 
purposes only. All persons who transport bulk LPG in interstate commerce 
could be identified from their registration statements for compliance 
purposes. Compliance inspectors, using statistical sampling methods, 
could make more inspections and, thus, could improve the potential effec- 
tiveness of their program. The safety record achieved by such transporters 
would be available to determine future risk levels, to evaluate the 
need for amendment to the regulations, and to evaluate the carriers' 
performances. The possibility of losing their safety registrations would 
act as a strong incentive for compliance with safety regulations. 

CONCLUSIONS 

Findings 

1. At a speed of 50 to 55 mph, the truck could not decelerate in time 
and was forced to swerve to the left to avoid the slowing automobile 
ahead. 

2. Had the posted speed limit been reduced and had the truck been 
traveling at a lesser speed, the evasive maneuver may not have been 
necessary, or if taken, may not have been so severe as to overturn 
the truck. 

3. The vehicles parked on the shoulder of the road in front of the 
used-car facility reduced the area in which the truckdriver could 
recover and left the truckdriver only one opportunity for evasive 
action. Their presence effectively eliminated the 30-foot roadside 
recovery area recommended by FHWA Highway Safety Program Standard 12, 
"Highway Design, Construction, and Maintenance." 

4. A protective barrier could not have prevented the tank from striking 
the concrete headwall, but it could have absorbed sufficient energy 
or redirected the tank so as to prevent the tank from rupturing. 

5. The concrete headwall should have been constructed in conformance 
with FHWA recommended practice and the AASHTO standard specification; 
if it had been flush with the ground, the severity of this accident 
would have been reduced. 

6. There were no identifiable preimpact defects in the tractor, the tank- 
semitrailer, or the tank that could have contributed to the accident. 

7. Persons in the used-car facility and in automobiles had no time 
to escape from the explosions and fire. 

8. Technical methods to reduce the casualties caused by the behavior 
of pressurized, liquefied LPG released from broken bulk containers 
in accidents need to be explored and have not been. 



- 15 - 



i 



The continuing possibility of catastrophic accidents during trans- 
portation of LPG in bulk requires that safety measures be developed 
to reduce the harmful effects of the sudden release of large quantities 
of pressurized, liquefied LPG. 

Probable Cause 

The National Transportation Safety Board determines that the probable 
cause of this accident was the evasive action taken by the truckdriver 
to avoid a slowing vehicle in his path of travel. The cause of the 
fatalities and injuries to persons in the vicinity was the explosive 
force and fire, from which they had no time to escape. The rapid develop- 
ment of the explosive force and fire was caused by the gross rupture of 
the tank. 

RECOMMENDATIONS 

As a result of its investigation of this accident, the National 
Transportation Safety Board made the following recommendations — 
— to the Federal Highway Administration: 

"Promulgate a regulation to require the criteria established in the 
Handbook of Highway Design for Operating Practices (E2 Culverts and 
Bridge Structures) be mandatory for all modified and new designs. 



I 



"Compile and evaluate accident data related to unprotected, raised 
concrete headwalls and sidewalls which, because of their location, 
are roadside fixed objects, to determine whether added emphasis for 
their modification or protection is warranted." 

— to the Texas State Department of Highways and Public Transportation: 

"Conduct an engineering survey on U.S. Route 277 between the 
intersection with U.S. Route 57 and the city limits of Eagle Pass 
to determine if a prohibition of parking on the shoulder of this 
high-speed highway or a reduction in the speed limit, or both, 
would reduce the traffic conflicts in this area; then, take appro- 
priate actions in accordance with the findings of the survey." 

— to the U.S. Department of Transportation: 

"Initiate a research program to identify new approaches to reduce 
the injuries and damages caused by the dangerous behavior of 
pressurized, liquefied flammable gases released from breached tanks 
on bulk transport vehicles." 



- 16 - 

"Establish a regulation to require the safety registration 
statements authorized by Section 106(b) of the Hazardous 
Materials Act of persons transportation bulk shipments of 
pressurized, liquefied petroleum gases in a form and quantity 
capable of causing widespread injury and property damage in 
transportation accidents." 

BY THE NATIONAL TRANSPORTATION SAFETY BOARD 

/s/ WEBSTER B. TODD, JR. 





Chairman 




/s/ FRANCIS H. 


, McADAMS 




Member 




/s/ ISABEL A. 


BURGESS 




Member 




li 


3/ WILLIAM R, 


. HALEY 




Member 




/'• 


3/ PHILIP A. 


HOGUE 



Member 



May 5, 1976 



- 17 - 



APPENDIX 



Investigation 



This report is based on an investigation by the National 
Transportation Safety Board under the authority of the Independent 
Safety Board Act of 1974. The Texas Department of Public Safety, 
the Bureau of Motor Carrier Safety (FHWA) , and the Railroad 
Commission of Texas participated in the investigation. 



DATE DUE 




^c3Cp6'7 



HV 8079.55 .U58 76-4 
Surtigas, S . A. , 
tank-semitrailer overturn, 
explosion, and fire, near 



D*Ti[_ r 



■onaawus maux 



HV 8079.55 .U58 76-4 
Surtigas, S . A. , 
tank-semitrailer overturn, 
explosion, and fire, near 



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